For women at high risk of breast cancer, it is important to help them realistically assess their decision making needs and access quality decision support resources so they can make informed, value-sensitive decisions about chemoprevention. This presents a timely clinical and public health opportunity to inform women about their breast cancer risk decisions and support their decision-making needs through an innovative web-based decision support intervention to complement clinical care, that is available whenever, wherever, and as often as needed during the decision-making period. The proposed project will be guided by the Cognitive-Social Health Information Processing model overall, and incorporate the Ottawa Decision Support Framework in one consistent decision support process. Specific aims are to: (1) Aim 1: Develop and refine a web-based patient decision support module for high-risk women making a decision about breast cancer chemoprevention, to be used as a prototype for designing a more comprehensive Trusted Advisor for Cancer Health Decisions (TACHD) decision support system, and (2) Aim 2: Conduct a formative evaluation of the impact of the chemoprevention module, which will include a pilot study and a process evaluation. For Aim 1, TACHD development will follow three phases that will result in: (1) functional HTML screens;(2) a fully functional intervention web site;and (3) an administrative functionality. They will be user- tested and usability tested with the target population. For Aim 2, pilot testing of the chemoprevention decision support module will be conducted in a two-group pre- post-test experimental design with 64 at-risk women identified through Fox Chase Risk Assessment Programs and the NCI Clinical Cancer Genetics Program at National Naval Medical Center. A process evaluation analysis will assess participants'experiences using TACHD. For aim 2 analyses, (1) two-sided two-sample paired t-tests will evaluate the impact of TACHD on changes in the primary outcome of decisional conflict, as well as decision stage, attentional style, cancer worry, cancer distress, and cancer risk perception;(2) two-sample, paired t-tests will identify discrete versions of psychological factors associated with differential changes in decisional conflict;and (3) potential moderator (attentional style) and mediator variables (cancer worry, cancer distress, cancer risk perception) will be explored. Decision support interventions such as TACHD can promote quality decisions -- defined as informed and consistent with personal values -- among individuals concerned about breast cancer risk and result in better public health outcomes such as improved risk reduction behaviors and lower cancer-related morbidity and mortality.